Review ArticleComparison of Clinical Efficacy and Anatomical Investigationbetween Retrolaminar Block and Erector Spinae Plane Block

Eiko Onishi , Noriko Toda, Yoshinobu Kameyama, andMasanori Yamauchi

Department of Anesthesiology, Tohoku University Hospital, Sendai, Miyagi, Japan

Correspondence should be addressed to Eiko Onishi; e-onishi@med.tohoku.ac.jp

Received 20 January 2019; Revised 2 March 2019; Accepted 5 March 2019; Published 28 March 2019

Guest Editor: Hironobu Ueshima

Copyright © 2019 Eiko Onishi et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Retrolaminar block (RLB) and erector spinae plane block (ESPB) are alternative approaches to paravertebral block (PVB) and areadvantageous in that they are easier and safer techniques compared with the traditional PVB. Many clinical reports of these blockshave described their efficacy for ipsilateral thoracic analgesia.The local anesthetic injection points of RLB and ESPB are the laminaand transverse process, respectively. Despite the similarity of the puncture sites, there have been no clinical studies comparing RLBand ESPB. In addition, the underlyingmechanism of these blocks has not been clarified. Recent anatomical investigations indicatedthat the injectate was distributed in the paravertebral space and spread laterally into the intercostal spaces.The limited distributioninto the paravertebral space indicated that compared to PVB, RLB and ESPB exert their effects via a different mechanism. In thisreview, we describe the features of and differences between RLB and ESPB based on current clinical and anatomical reports. Wealso propose the clinical indication and discuss the differences, clinical outcomes, and anatomical mechanisms of the techniques.

1. Introduction

For an ideal perioperative regional anesthetic technique,mostanesthesiologists would prefer a safe, easy, and minimallyinvasive procedure that can be performed in a shorter timeframe and provide appropriate analgesia. The developmentof ultrasonography led to the establishment of ultrasound(US-) guided nerve blocks. US-guided nerve blocks are nowcommonly used as a part of the multimodal postoperativeanalgesic strategy. Various approaches to US-guided periph-eral nerve block (PNB) have been reported recently [1–6],including intramuscular, compartment, and interfascial planeblocks.The site of injection is not the perineural space but thespace throughwhich the peripheral branch of the target nerveruns.

Thoracic epidural anesthesia (TEA) and paravertebralblock (PVB) have been used to provide perioperative regionalanesthesia in the trunk. However, TEA is technically difficultin some cases, and is associated with a risk of seriouscomplications, such as epidural hematoma, nerve injury, andhypotension. PVB has the advantage of visualization of theneedle position using ultrasonography. However, PVB is also

associated with a risk of serious complications, such as pneu-mothorax, hypotension, or nerve injury. Newer approachesto PVB have been the focus of many studies in recent years;these approaches include retrolaminar block (RLB) [5] anderector spinae plane block (ESPB) [6]. These blocks areconsidered to be compartment blocks or interfascial planeblocks. In these approaches, local anesthetics are assumed topenetrate the superior costotransverse ligament and reach theparavertebral space, although the needle tip is not advancedinto the paravertebral space (Figure 1). The clinical effectof RLB and ESPB has been reported for ipsilateral thoracicsurgery. Further, considering the close puncture sites of RLBand ESPB (Figure 1), the similarities between RLB and ESPBhave been discussed previously [7, 8]. However, the injectatedistribution patterns and the mechanisms of spinal nerveblockade of both techniques remain unclear. Anatomicalevidence may be crucial to aid our understanding of thenature of these blocks.

In this review, we demonstrate the features and differ-ences with regard to the clinical efficacy and anatomicaldistribution of RLB and ESPB. We also aim to clarify theappropriate indications for RLB and ESPB.

HindawiBioMed Research InternationalVolume 2019, Article ID 2578396, 8 pageshttps://doi.org/10.1155/2019/2578396

2 BioMed Research International

AV

RLB

pleura

paravertebral space

superior costotransverse ligament

ESPB

Figure 1:�e injection point of the retrolaminar block and erector spinae plane block. The needle used for retrolaminar block (RLB) is inserted1 cm lateral to the spinous process and local anesthetic is injected on the lamina. The needle used for erector spinae plane block (ESPB) isinserted 2-3 cm lateral to the spinous process and local anesthetic is injected on the transversus process. In both RLB and ESPB, the needle isnot required to penetrate the superior costotransverse ligament.

RLB ESB

cranial cranialcaudal caudal

lamina

transversusprocess

RLBESPB

Figure 2: Ultrasound images of retrolaminar block and erector spinae plane block. The sagittal plane with a linear ultrasound probe allows forvisualization of the laminae or transversus process. The insertion points for retrolaminar block (RLB) and erector spinae plane block (ESPB)are similar. The transversus process is more superficial than the lamina in the ultrasound image, and the injection point for ESPB is close tothe pleura.

2. RLB and ESPB Techniques

RLB was first reported in 2006 as an alternative approach toPVB [9]. RLB is performed with US imaging or the landmarktechnique. The needle is inserted at a puncture site 1-1.5 cmlateral to the target spinous process and advanced caudallyor cranially until it contacts the lamina (Figure 1). Localanesthetics are injected on the lamina at doses of 20-30 ml.

ESPB was first reported in 2016 for ipsilateral thoracicanalgesia [6]. The needle is inserted at a puncture site 2-3 cmlateral to the target spinous process using US imaging andadvanced until contact is made with the transverse process(Figure 1). The needle-tip in ESPB is advanced to a moresuperficial point than that in PVB; thus, visualization of theneedle using ultrasonography is considered to be easier inESPB than in PVB.The local anesthetic (20-30 ml) is injectedbetween the transverse process and the erector spinaemuscle.

These two compartment blocks can be performed withthe US-guided, in-plane insertion technique. The sagittalplane with a linear US probe allows for visualization of thelaminae or transversus process (Figure 2), and the needleis advanced using the in-plane technique. With regard tocomplications, only one case report of pneumothorax afterESPB has been reported [10]. ESPB cannot be performedwith the landmark technique, because the transverse processis not detected by palpation. Hence, using ultrasonographyis essential in ESPB. However, RLB can be performed withthe landmark technique. The needle can be advanced to thelamina and the target spinous process can be palpated, similarto the paramedian approach in thoracic epidural puncture.The technique of RLB is simpler and easier than that of ESPB.We also previously recommended that the RLB needle beadvanced perpendicular to the skin or cephalad to caudal inorder to avoid epidural injection [11]. No complications ofRLB have been reported.

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Table 1: The features of RLB, ESPB, PVB, and TEA.

RLB ESPB PVB TEADifficulty probably easy advanced levelTechnique

Methods landmark or ultrasound ultrasound ultrasound landmarkNeedle-tip position lamina transversus process paravertebral space epidural space

Laterality of effects unilateral unilateral unilateral bilateral

Complications

rare rare hypotension epidural hematoma(less than TEA) epidural abscesspneumothorax paralysis

epidural injection nerve injuryhematoma hypotension

dural punctureRLB: retrolaminar block, ESPB: erector spinae plane block, PVB: paravertebral block, and TEA: thoracic epidural anesthesia.

3. Comparison of RLB and ESPB withPVB and TEA

The technical features of RLB, ESPB, PVB, and TEA aresummarized in Table 1. TEA is the most common techniqueand provides both somatic and visceral analgesia. However,the failure rate is reported to be 14-30% [12]; significant skilland experience are needed to perform TEA. The compli-cations associated with TEA are accidental dural puncture,hypotension, spinal injection, nerve injury, and epiduralhematoma [12]. In contrast, US-guided PVB was reported tobe associated with very few complications [13]. However, theneedle-tip must be close to the pleura and spinal nerve roots.PVB has been classified as a technique of advanced level ofdifficulty [14].

The advantage of RLB and ESPB is that they are tech-nically easier procedures than PVB and TEA. The needle-tip of RLB and ESPB is not closer to pleura and spinalnerve roots than that of TEA and PVB. Furthermore, usingUS images allows for visualization of the needle and localanesthetic distribution. However, the available informationregarding these blocks is not sufficient; the optimal doseof local anesthetics, area of sensory block, and differencesbetween single and multilevel injection or single injectionand continuous injection remain to be clarified.

4. Clinical Reports

Clinical case reports on both RLB and ESPB have demon-strated the efficacy of these techniques. However, only a fewrandomized controlled trials (RCTs) have investigated RLBand ESPB.

The efficacy of continuous RLB has been reported forbreast cancer surgery [15, 16] and rib fracture [5, 17]. Thesereports of successful cases indicated RLB to be an effectivemethod as an alternative to PVB or multiple intercostalnerve blocks. However, some reports questioned whetherRLB offers an analgesic effect equivalent to that of PVB.Satoh demonstrated that the mixtures of local anesthet-ics and contrast dye were distributed across the laminaecephalocaudally and did not disperse into the paravertebral

space in a radiographic study [18]. Additionally, Murouchiet al. evaluated the use of continuous RLB for breast cancersurgery as compared with PVB [19]. They reported thatthe analgesic effect of RLB was weaker than that of classicPVB. We previously reported an RCT of single-shot RLBfor breast cancer surgery [11], which is the only RCT ofRLB. We found that the use of RLB did not reduce thenumber of patients requiring postoperative analgesia, and thepostoperative analgesic duration was only 2-3 h, which wasunexpectedly shorter than that of PVB reported previously. Inour study, we performed RLB without ultrasonography andinjected a lower volume of local anesthetics at two sites: 15 mlat T2 and T4, respectively. These methods could potentiallyhave influenced our results.

However, the efficacy of ESPB has been described ina greater number of clinical reports than has RLB: a ribfracture [20], breast surgery [21, 22], thoracoscopic surgery[23, 24], lumbar spinal surgery [25, 26], and laparoscopicabdominal surgery [27, 28]. In contrast to RLB, the majorityof the literature on ESPB reported the use of the single-shottechnique (80.2%) [29]. The local anesthetic was postulatedto infiltrate the ventral and dorsal rami of the spinal nerve.However, Ueshima et al. reported that ESPB could notprovide adequate analgesia of the anterior branch of theintercostal nerve [30]. Therefore, the mechanism of ESPB asa PVB is controversial.

In 2018, three RCTs of ESPB were reported. Tulgar etal. evaluated the postoperative analgesia provided by ESPBin laparoscopic cholecystectomy [28]. They demonstratedthat bilateral single-shot ESPB performed before generalanesthesia induction significantly reduced postoperative painin the initial 3 h and the requirement for postoperativeanalgesia in the initial 24 h compared with the generalanesthesia alone technique. Gurkan et al. also demonstratedthat the preoperative single-shot ESPB reduced the postop-erative morphine consumption within 24 h after surgery inpatients undergoing breast cancer surgery [21]. Additionally,Krishna et al. demonstrated that the bilateral ESPB for cardiacsurgery provided significantly superior analgesia in the acutepostsurgical phase and a longer duration of analgesia thanthat provided in the control group [31]. Although these RCTs

4 BioMed Research International

were single-blinded studies, they demonstrated the clinicalefficacy of single-shot ESPB.

The clinical case reports on RLB and ESPB indicatedtheir potential as alternative methods of PVB and TEA. TheRCTs reported that the clinical efficacy of single-shot RLBwas controversial, while ESPB resulted in significantly lowerpostoperative pain. However, no reports have compared RLBand ESPB or investigated the optimal dose and concentrationof local anesthetics. High quality randomized trials areneeded to evaluate clinical efficacy of RLB and ESPB.

5. Anatomical Studies

In 2016, Costache et al. reported that the superior costo-transverse ligament was not a barrier to the diffusion of theinjectate, and local anesthetics could penetrate the ligamenttoward the paravertebral space [32]. This report supportedthe hypothesis that the local anesthetics injected in RLBor ESPB would penetrate the paravertebral space. Subse-quently, in 2018, several cadaveric anatomical investigationswere reported, which provided meaningful results for theclarification of themechanisms ofRLB andESPB [33–35].Theanatomical investigations are summarized in Table 2.

Initially, Ivanusic et al. performed a cadaveric experi-ment to determine whether the injectate of ESPB dispersedanteriorly into the paravertebral space [33]. They injected20 ml of 0.25% methylene blue dye into the plane betweenthe fifth thoracic transverse process and the erector spinaemuscle of unembalmed cadavers.They demonstrated that theinjectate was distributed craniocaudally and laterally alongthe erector spinae muscles, and the dorsal ramus was stainedwith dye. However, the paravertebral space and intercostalnerves were not stained with dye. They also demonstratedthat the extensive lateral diffusion of local anesthetics couldinvolve the lateral cutaneous branches of the intercostalnerves, which allowed wide cutaneous sensory block of thehemi-thorax.

In contrast, Adhikary et al. performed a comparativestudy of the distribution of 20ml of injectate of RLB andESPBin fresh cadavers, using both magnetic resonance imagingand anatomical dissection [34]. Single-shot RLB and ESPBboth produced epidural andneural foraminal diffusion acrosstwo to five vertebral levels centered around the level ofinjection, which indicated that both techniques elicit clinicaleffects similar to those of PVB. In particular, the injectateof ESPB was dispersed more widely into the intercostalspace than was RLB. ESPB could provide analgesia of theanterolateral thoracic and abdominal wall as an intercostalnerve block.

Sabouri et al. also investigated the distribution of localanesthetic after RLB using unembalmed, fresh frozen, andthawed cadavers [35] using injection of 20ml of amixture of 1ml of 1%methylene blue and 19 ml of 0.5% bupivacaine.Theydemonstrated that the injectate of the retrolaminar spacecould diffuse into the paravertebral space, epidural space,and intervertebral foramina.However, the pattern of injectatedispersion in RLB was variable, and the diffusion into theparavertebral spacemight bemore limited than that of classicPVB.

Additionally, Yang et al. demonstrated that the injectatesof RLB and ESPB reached the paravertebral space and infil-trated the superior costotransverse ligament in unembalmedcadavers [36]. The area stained with dye in ESPB was morelateral, whereas the dye spread vertically along the posteriorsurface of the lamina in RLB. These findings indicated thatRLB could involve the dorsal rami of the spinal nerve andmay be more suitable for the analgesia of the thoracic backregion than is ESPB.

In these anatomical investigations, the difference in thetissue condition between a cadaver and a living person wasdescribed as a limitation. The possibility that tissue manip-ulation during dissection could have caused dye dispersionto deeper areas such as the epidural space and paravertebralspace was also not excluded. Thus, the anatomical mecha-nisms of RLB and ESPB have not been fully clarified. Theareas of injectate distribution in both RLB and ESPB differedamong studies. However, the patterns of injectate distributioncan be summarized according to the following three points.First, the dye in RLB was distributed vertically beneath thetransversospinalis muscles, and the dorsal rami of spinalnerve could be blocked. Second, the dye in ESPB spreadlaterally, and the intercostal nerve or the lateral cutaneousbranches of intercostal nerve could be blocked. Finally, thedistribution into the paravertebral space was limited in bothRLB and ESPB.

6. Anatomical Mechanism as an InterfascialPlane Block

Elsharkawy et al. reported very interesting findings regardingthe interfascial plane block [37]. They described that theretrolaminar space and erector spinae muscle plane aredirectly linked to the interfascial plane, through which thelateral cutaneous branch runs. If the local anesthetics injectedin RLB or ESPB are distributed in the interfascial plane,the blockade of the lateral cutaneous branch can providehemithoracic analgesia. This report suggested that RLB andESPB would have a mechanism as an interfascial plane block.Ivanusic et al. also visualized the small branches of theintercostal nerves running through the external intercostalmuscle layer in an anatomical investigation [38]. If thelocal anesthetics injected via RLB or ESPB were laterallydistributed as an interfascial plane block in a live body, thesesmall branches would be infiltrated, which could providehemithoracic analgesia (Figure 3).

Summarizing these anatomical investigations and litera-ture regarding interfascial plane block, RLB and ESPB couldhave two mechanisms; “the PVB pathway” and “the lateralpathway.” Firstly, the PVB pathway involves both ventraland dorsal spinal rami. However, the limited distribution oflocal anesthetics can cause the potency of RLB and ESPB tobe weaker than that of PVB. Secondly, the lateral pathwayinvolves the lateral cutaneous branch and small branches ofintercostal nerves. The blockade of these cutaneous branchesof intercostal nerves can provide a certain level of analgesiafor the hemithorax. The injectate of ESPB is distributeddeeper and more lateral than that of RLB. Therefore, ESPBis likely to produce larger area of anesthesia than that of RLB.

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Table2:Th

ecom

paris

onof

anatom

icalinvestigations.

Ivanusicetal.

Adhikary

etal.

Sabo

urietal.

Yang

etal.

Targetof

theinvestig

ation

ESPB

RLBandES

PBRL

BRL

BandES

PBMetho

d20

injectionin

10cadavers

3injectionpere

achblock

8injectionin

8cadavers

10injectionpere

achblock

Cadaver

unem

balm

ed/freshcadavers

Injectionlevel

T5vertebrallevel

T5vertebrallevel

T4vertebrallevel

T5vertebrallevel

Injectatev

olum

e20

mlofm

ixture

Thes

preadof

dye

Anterior

Paravertebralspace

none

possiblein

both

blocks

possible(quitevaria

ble)

limitedspread

Epiduralspace

nodetails

Intercostalspace

nodetails

Poste

rior

Thed

orsalram

uswas

frequ

ently

stained.

RLB:

beneaththe

transversospinalismuscle

sES

PB:beneath

thee

rector

spinae

muscle

s

Thed

yespread

beneaththe

paraspinalmuscle

s.

RLB:

thes

urface

ofthe

transversospinalismuscle

ESPB

:the

surfa

ceof

thee

xternal

intercostalm

uscle

Lateral

Thed

yeoft

enspread

tothe

attachmentsof

iliocostalis

muscle

.

ESPB

>RL

BRL

B:to

thee

dgeo

fthe

bony

lamina

ESPB

:extending

9to

10cm

lateral

medianlateralspread2.5cm

RLB<ES

PBRL

B:lim

itedmedially

totheintertransverse

ligam

ents

ESPB

:spreadto

iliocostalis

muscle

Long

itudinal

Them

ajority

ofthed

yespread

was

ceph

alad

toT6

.

ESPB

>RL

BRL

B:6-9vertebrallevels

ESPB

:9-14vertebrallevels

medianceph

alad

spread

3.5cm

caud

adspread10.7cm

spinalnerveinvolvement:

RLB(2

levels)

>ES

PB(3.5levels)

RLB:

retro

laminar

blockandES

PB:erector

spinae

planeb

lock.

6 BioMed Research International

lateral branch ofintercostal nerve

serratus anteriormuscle

ventral rami ofspinal nerve

dorsal rami ofspinal nerve

external intercostalmuscle

internal intercostalmuscle

innermost intercostalmuscle

PVB pathway

erectorspinaemuscle

Lateral pathway

Figure 3: �e distribution pathway of local anesthetics in retrolaminar block and erector spinae plane block. The paravertebral block (PVB)pathway involves both the ventral and the dorsal spinal rami and showed similar mechanism with PVB. The lateral pathway involves thelateral cutaneous branch and small branches of intercostal nerves. This pathway was similar to the mechanism underlying interfascial planeblock.

7. Future Investigations and ClinicalIndications

Anatomical studies have demonstrated restricted distributionof dyes in both RLB and ESPB in the paravertebral space,which indicates that the analgesic adequacy of the two blocksmight be less certain than that of PVB and TEA.The optimaldose and volume of local anesthetics for RLB and ESPB havenot been elucidated. A recent anatomical study of RLB usingporcine cadavers suggested that the dye was distributed to theparavertebral space in a volume-dependent manner [39]. DeCassai et al. also evaluated the volume of local anesthetics inESPB. They demonstrated that a median volume of 3.4ml oflocal anesthetic was required to anesthetize one dermatome.The volume of local anesthetics will be an important factorin determining the anesthetized area for both RLB and ESPB.Further investigation regarding the optimal dose and volumeof local anesthetics and the sensory block area is necessary toestablish the techniques of RLB and ESPB.

In anatomical studies, the dye injected via an RLB tendsto infiltrate the dorsal rami of the spinal nerve, and thelateral pathway is not involved in the main mechanism ofRLB. Technically, RLB is easy and safe and can be performedwithout ultrasonography. RLBwill be suitable for ambulatorypatients or patients with back pain. In contrast, the lateralpathway is the main mechanism of ESPB. The blockade ofthe intercostal nerve or the lateral cutaneous branches ofthe intercostal nerves would provide hemithoracic analgesia.

Therefore, ESPB will be useful for perioperative analgesia inhemithoracic surgery. However, the PVB pathway of RLB andESPB is varied and restricted; hence, these blocks could not bea solo anesthesia technique for thoracicwall surgery. TEAandPVB should also be performed for supplemental analgesia,if adequate analgesia cannot be achieved using these twoblocks.

8. Conclusion

We reviewed the clinical features and anatomical findings ofRLB and ESPB. The advantages of these techniques are thatthey are easy and have low risks of severe complications. Theanatomical investigations demonstrated that the distributionof the injectate in RLB and ESPB follows the PVB pathwayand the lateral pathway. However, the mechanisms of RLBand ESPB have not been fully clarified. The clinical efficacypresented in reports including case reports and controlstudies suggests that these blocksmay be potentially useful foranesthesiologists. However, only a fewRCTs of RLB andESPBhave been reported. To establish RLB and ESPB as routineprocedures in the clinical setting, high-quality RCTs will beessential in the future.

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this article.

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Acknowledgments

This research was supported by AMED under Grant NumberJ180000588.This work was partially supported by the TohokuUniversity Center for Gender Equality Promotion (TUMUG)Support Project (Project to Promote Gender Equality andFemale Researchers).

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